Stabilized impeller



April 4, 1961 K. DAVEY 2,978,233

STABILIZED IMPELLER Filed March 24, 1958 2 Sheets-Sheet 1 KINGSLE)DAVE):

April 4, 1961 K. DAVEY 2,978,233

STABILIZED IMPELLER Filed March 24, 1958 2 Sheets-Sheet 2 Ah/zwromKINGSLEY 0A V531 STABILIZED lM'PELLER Kingsley Davey, 72 WhitehallCourt, St. Louis 17, Mo.

Filed Mar. 24, 1958, Ser. No. 723,406

7 Claims. (Cl. 259-96) The present invention relates generally to liquidmixing devices, and more particularly to'a novelstabilized impeller forproviding an improved mixing action with a minimum tendency to gyrate orwhiplaround its normal axis of rotation;

Briefly, it has been found that a conventional impeller mounted at thefree end of a rotating shaft for stirring liquids in a vatytank, orsimilar container almost always tends to revolve in an orbit about thenormal axis of the rotating parts. Past efforts to overcome thistendency toward undesirable whipping have included both the employmentof an oversize shaft for mounting the impeller and the addition of alower guide bearing for the shaft. An oversize shaft, however, willincrease the weight of the stirring apparatus andwillalso impair itsmixing efficiency, besides being costly where conditions require theshaft tobe of expensive alloy metal. The use of a submerged bearing, onthe other hand, provides obvious difliculties of service andmaintenance.

It is an object of the present invention, therefore, to

'provide a novel liquid mixing impeller which largely overcomes anytendency towhip.

It is another object of the invention to provide a novel liquid mixingimpeller adapted to be mounted at the free end of a. relatively slenderrotatable shaft and having self-stabilizing operating characteristics.

It is another object of the invention to provide a novel liquid mixingimpeller adapted to develop a liquid pressure differential which iseffective to overcome whipping tendencies in the impeller.

It is another object of the invention to provide a novel liquid mixingimpeller incorporating radially extended blades surmounted by ahub plateand having an underlying stabilizer ring.

It is another object of the invention to provide a novel liquid mixingimpeller provided with axially spaced stabilizer rings.

The foregoing, along with additional objects and advantages, will beapparent from the following description of a preferred embodiment of theinvention.

' In the drawings: a

Figure 1 is a top plan view of an impeller constructed in conformancewith the present invention;

Figure 2 is aside elevation thereof, portions being broken away in orderto disclose details shown in fragmentary section;

Figure 3 is a vertical section taken generally along the line 33 ofFigure 1', the impeller being illustrated in mounted position at thefree end of a vertical shaft shown fragmentarily;

Figure .4 is an isometric View of a removed spoke;

Figure 5 is a plan view of a'removed bracket;

Figure 6 is a side elevation thereof;

Figure 7 is a diagrammatic representation of the impeller of Figure 1in, typical use as a stirring device;

Figure 8 is a top plan view of another impeller con structed inconformance with the present invention;

Figure 9 is a vertical section taken generally along 2,978,233 PatentedApr. 4, 1961 the line 9-9 of Figure 8, the impeller being illustrated inmounted position at the free end of a vertical shaft shownfragmentarily; and

Figure 10 is a diagrammatic representation of the impeller of Figure 8in typical use as a stirring device.

Referring more particularly to the drawings by means of the referencenumerals shown thereon, the numeral ll) designates generally one type ofstabilized impeller constructed in accordance with the teachings of thepresent invention. The impeller it) includes a hub 12 provided with acentral bore 14 for receiving a rotatable shaft 16. Keyways l8 and 20formed in the hub 12 and in the shaft 16, respectively, accommodate anelongated key 22 retained by means of a set screw 24 inserted through athreaded hole 26 in the hub 12.

A plurality of spokes 28 disposed equidistantly about the periphery ofthe hub 12 are secured to the latter, as by welding, so as to extendradially therefrom as clearly indicated in Figure l. The spokes 28 hereillustrated take the form of flat plates, as illustrated in Figure 4.Preferably, the spokes 28 are disposed at an inclination to a planeperpendicular to the axis of rotation of the hub 12, whereby they mayserve as vanes for accommodating a vertical flow of liquid as theimpeller It) is rotated. This arrangement of the vanes or spokes 28 isshown clearly in the sectional view of Figure 3. An upper stabilizingring 3t having the form of a relatively short cylindrical sleeve issecured, as by welding, to the outer ends of the severalspokes 28 so asto be concentric with the hub 12.

The impeller 10 includes an even number of peripheral blades comprisingequal but alternately pitched pluralities of downwardly directed blades32 and upwardly directed blades 34. The blades 32 and 34 are generallyindicated, in this instance, taking the form of arcuately bent straps.They differ, however, in having their inner ends beveled at oppositeangles for achieving the aforementioned upward and downward dispositionrelative to their main plane of rotation. Thus, each blade 32 and 34 isprovided at its inner end with both an upper blade bracket 36 and alower blade bracket 38, these brackets being identical, except ofopposite hand. An upper blade bracket 36, shown removed in Figures 5 and6, is seen to comprise an arcuate base plate lit and a side gusset 42.The curvature of the base plate 40 corresponds to the outside of thestabilizing ring 30, and matching holes are provided in these membersfor receiving bolt assemblies 44.

As is clear from the illustration, the several blades 32 and 3:4 aresupported from the upper stabilizing ring 30 by bolted attachment of theblade brackets 36 thereto. The lower blade brackets 38 are similarlysecured to a lower stabilizing ring 46, similar in size and shape to theupper stabilizing ring Ml. Between the rings 30 and 46 is an open space48.

Figures 8 through 10 of the drawings illustrate an impeller 54), alsoconstructed in accordance with the teachings of the present invention,but of modified form relative to the above-described impeller ltl.

The impeller 56 differs from the impeller 16 primarily in having a solidhub plate 52 surmounting the blade structure at the inner ends of theblades in place of an upper ring such as the ring 30 in the impellerill. Thus, as is clear from Figures 8 and 9, the hub plate 52 forms asolid annulus integral with the lower end of a hub 54 having a centralbore 56 for receiving a rotatable shaft 53. Keyways 6i) and 62 formed inthe hub 54 and in the shaft 58, respectively, accommodate an elongatedkey 64 retained by means of a set screw 66 inserted through a threadedhole 67 in the hub 54.

The impeller 50 has an even number of peripheral blades comprising equalbut alternately pitched pluralities 3 of downwardly directed blades 68and upwardly directed blades 70. As here illustrated, the blades 68 and70 take the general form of straight blades given a backward sweep, aswell as an upward or downward twist, from points adjacent theirattachment to the hub plate 52. Each blade'68 or 70 is provided with aradially inwardly extending tab 72 at its upper edge and a downwardlyextending tab 74 formed arcuately as clearly shown in Figure 8. Thesetabs 72 and '74 form integral portions of the blades 68 and 70 anddiffer from one another oni y in being adapted to conform to the upwardor downward twist of their respective blades.

The blades 68 and 70 are secured in alternation to the hub plate 52 bymeans of bolt assemblies '76. The lower tabs 74 of the blades aresimilarly secured to a stabilizing ring 78 disposed in coaxial relationto the extended axis of the shaft 58.

Each of the stabilizing rings 30, 46 and 78 is defined by the rotationof a thin rectangle about the relatively distantly spaced hub axis, asis obvious from the drawings.

In use, either the impeller or the impeller 54) is normally secured tothe lower end of a shaft, such as the shafts 16 or 58, and then disposedin a tank T containing a liquid L to be agitated or mixed. Thisarrangement, depicted diagrammatically in Figures 7 and 10, enables theparticular rotating impeller to provide an efficient mixing actionresulting from the form and relative disposition of its oppositelyupwardly and downwardly directed blades. Of particular significance inthe present invention, however, are the forces which prevail centrallyor inwardly of the blades of the impellers 10 and 50.

Directing attention to this area, therefore, and noting the majorcurrents of flow within the tank T as indicated generally by thedirectional arrows of Figures 7 and 10, it is evident that liquid L iscaused to move downwardly at the center of the tank T along the shafts16 and 58 toward the impeller hubs. At the same time, liquid rises fromthe region directly below the centers of the impellers. In the case ofthe impeller 10, the downward flow continues through the upperstabilizing ring 30 to meet the upward flow through the lowerstabilizing ring 46. These two currents of flow merge at the open space48 between the rings 30 and 46 and the resulting outwardly expandingmerged flow is picked up by the inner ends of the blades 32 and 34- foroutward propulsion.

It may be noted that the inclined arrangement of the spokes 28 in theimpeller 10 is primarily for conformance with the above-described flowpattern, and not for instigating or maintaining it. In other words, theprimary function of the spokes 28 is to support the portions of theimpeller 10 outwardly of the hub 12 without inhibiting or restrictingthe aforementioned flow pattern. It is recognized, however, that undercertain circumstances it may be desirable to avail the impeller 10 offlow impetus obtainable from the vane-like spokes 28. To this end, then,it is apparent, not only that the vanes 28 may be positioned indifferent attitudes, but also that similar vanes may be incorporated inthe lower stabilizer ring 46.

The impeller 54), as previously indicated, eliminates the upper openring corresponding to the ring 30 in the impeller 10 and providesinstead the solid hub plate 52. The effect of this is to deflect thedownwardly moving central current of liquid before it meets the upwardlymoving current that rises through the lower ring 78. As a result, thedeflected downwardly moving current enters the blade region from aboveand is directed generally toward the lower corners 80 of the tank T.Thus, the impeller 50 is particularly useful where corner scouringaction is necessary to prevent pile-up of solids in the corners 80. Byproper placement of the impeller relative to the lower tank corners,along with appropriate proportioning of tank and impeller sizes, aneffective cooperation is obtained which results in improved efliciencyof mixing.

Under any of the flow conditions described above, it is evident that aconstant static liquid pressure will normally prevail at the outersurfaces of the stabilizer rings 30, 46, and 78. A different pressurewill exist within these rings, however, due to the relatively highvelocity of fluid flow therethrough. It has been found in respect toboth the impeller 10 and the impeller 50 that this pressure differentialbetween the inside and the outside of the rings 30, 46, and 78 provideseffective stabilization which overcomes any tendency of the impellers togyrate or whip. This stabilization not only increases the mixingefficiency, but also extends the life of the rotating parts.

Clearly, there has been provided a stabilized impeller which fulfillsthe objects and advantages sought therefor.

It is to be understood that the foregoing description and theaccompanying drawing have been given by way of illustration and example.It is further to be understood that changes in form of the elements,rearrangement of parts, and the substitution of equivalent elements, allof which will be apparent to those skilled in the art, are contemplatedas being within the scope of the present invention, which is limitedonly by the claims which follow.

What is claimed is:

1. A stabilized impeller of the kind described adapted to materiallyreduce shaft whip comprising a shaft receivable hub; a hollowcylindrical stabilizing member defined by the rotation of a thinrectangle about the relatively distantly spaced hub axis and spacedaxially from,

but coaxial with, said hub, the space between said cylinder and said hubbeing axially open and being in communication through said cylinder withthe axial extremity of said cylinder; means connecting said cylindricalmember to said hub; and a plurality of spaced blades carried by said huband extending between said hub and said cylinder and extending freelybeyond said cylinder and hub in a generally radial outward direction.

2. The impeller of claim 1 wherein the blades, hub and cylinder arerotatable as a unit.

3. A stabilized impeller of the kind described adapted to materiallyreduce shaft whip comprising a shaft receivable hub; a cylindricalstabilizing member defined by a thin cylindrical wall and spaced from,but coaxial with, said hub; means connecting said cylindrical member tosaid hub; and a plurality of spaced blades attached to and extendingbetween said hub and said cylindrical stabilizing member and radiallyoutwardly therefrom; said hub being flared to a diameter approximatelyequal to a diameter of said cylindrical stabilizing member.

4. A stabilized impeller of the kind described adapted to materiallyreduce shaft whip comprising a shaft receivable hub; a first cylindricalstabilizing member defined by a thin cylindrical wall and spaced axiallyfrom, but coaxial with, said hub; a second cylindrical stabilizingmember, the space between said first cylindrical member and said secondcylindrical member being axially open and being in communication througheach cylindrical member with the respective axial extremity of saidcylindrical member defined by a -thin cylindrical wall coaxial with andspaced axially from said first cylindrical stabilizing member; meansdrivingly connecting said cylindrical members to said hub; and aplurality of spaced blades attached to one of said cylindricalstabilizing members and extending between said cylindrical stabilizingmembers and extending freely beyond said cylindrical members in agenerally radial outward direction.

5. The impeller of claim 4 in which the cylinders are attached to thehub by spokes.

6. A stabilized impeller of the kind described adapted to materiallyreduce shaft whip comprising a shaft; a stabilizing cylinder defined bya thin cylindrical wall coaxial with and radially spaced from saidshaft; a hub attached to said shaft and forming a top for saidstabilizing cylinder; means connecting said cylinder to. said hubi aplurality of spaced impeller blades mounted between said cylinder andsaid top and serving to space said cyllizing sleeve circumscribing thespoke means, a second 15 thin-walled cylindrical stabilizing sleevedisposed coaxially with the first-mentioned stabilizing sleeve andaxially wholly beyond the innermost ends of the impeller blades andmeans drivingly connecting said sleeves to said hub.

References Cited in the file of this patent UNITED STATES PATENTS1,031,666 Richmond ..4 July 2, 1912 2,697,589 Davey Dec. 21, 19542,816,744 Penther Dec. 17, 1957 FOREIGN PATENTS 872,198 Germany Mar. 30,1953 365,420 Great Britain Jan. 21, 1932 607,392 Great Britain Aug. 30,1948

